A longitudinal study of 50 married couples is proposed that will obtain synchronized video and physiological data in a standard social psychophysiology laboratory and for 35 hours in a new apartment laboratory that will increase the naturalistic quality of the interaction. The gains expected from this new laboratory are particularly in the study of positive affect, which has been very difficult to simulate in the standard social psychophysiology laboratory. This will make it possible to study the potential health-inducing as well as illness-producing affective processes in marriages. Interaction will also be studied in a standard social psychophysiology laboratory. In addition, 24-hour urinary assays of stress related hormones, and in-vitro immunological measures of peripheral bloods as well as in-vivo measures of immune functioning in response to a harmless antigen will be assessed. Concurrent variation as well as longitudinal change in marital satisfaction, health, and marital interaction patterns will be outcome variables of the study. Process variables are physiological arousal during marital interaction, emotional behavior, listener withdrawal from interaction, gender differences in arousal in response to negative affect, gender differences in recovery from physiological arousal, soothing, and endocrine and immune assays.